<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head>
    <style type="text/css">
        html, body {
            height: 100%;
            margin: 0;
            padding: 0;
        }

        .wrap {
            width: 100%;
            height: 100%;
        }

        .fixed {
            float: left;
            width: 200px;
            height: 100%;
            background: #000;
            margin-left: -100%;
        }

        .main {
            float: left;
            width: 100%;
            height: 100%;
        }

        .main-inner {
            margin-left: 200px;
            background: #f00;
            height: 100%;
        }
    </style>

</head>

<body>

<div class="wrap">

    <div class="main">

        <div class="main-inner">

            test

        </div>

    </div>

    <div class="fixed">a</div>

</div>

</body>

</html>